My friends always hate it when I multi-task in other tabs while chatting with them (they can tell because of my obviously delayed reactions...). But sometimes it's not my fault: if they send me a link to a YouTube video, I have to open another tab in order to watch it. To help with this, we've just added a new feature to Gmail chat: YouTube and Google Video previews. If you receive (or send) a link to a video in a chat message, you'll see a preview of the video right in your chat window.

Click the preview, and the video will play right there. Just remember to say something every once in a while or your friends will probably catch on that you're enjoying the dramatic chipmunk more than their conversation...